In recent years, a number of factors have necessitated fundamental changes in the approach to automotive structural design. These include the need to meet ever-increasing impact resistance and fuel economy standards and the need to produce a competitively priced vehicle in a global marketplace. At times, these requirements are seemingly at odds with one another. For example, impact resistance can in most cases be achieved simply by increasing steel thickness or through the use of high strength steels. These approaches, however, generally increase vehicle weight and/or cost. Although light-weight resins are available which can be used to fill entire hollow cavities of structural members to provide greater strength, these materials are expensive and thus their use in great quantities undesirably increases vehicle cost.
The present inventor has pioneered a novel approach to structural part reinforcement through localized reinforcement of critical regions using microsphere-filled thermally expandable resins, such as: a composite door beam which has a resin-based core that occupies not more than one-third of the bore of a metal tube; a hollow laminate beam characterized by high stiffness-to-mass ratio and having an outer portion which is separated from an inner tube by a thin layer of structural foam, a W-shaped carrier insert reinforcement which carries a foam body for use in reinforcing a hollow beam; a bulkhead that utilizes a thermally expandable foam to provide localized reinforcement of a rail for the attachment of an engine cradle or the like.
Although these techniques are well suited for a number of applications, there exists a need for localized reinforcement of regions having special access problems. More specifically, in a number of hollow structural parts the member has an enclosed region or space which is located some distance from the opening of the space and is difficult to reach due to a curvature or bend in the member. In some instances the member and the channel which it defines have an irregular geometry that makes access to a particular internal region difficult. Of course, in some instances it may be possible to simply fill the entire structure with a liquid resin which is then cured, but as stated above, this approach may be prohibitively expense in a number of applications. Accordingly, there is a need for an alternative method of providing localized reinforcement of such parts. The present invention provides a solution to this problem.
It is an object of the present invention to provide a method of providing a local reinforcement in a region of a hollow structural part which is difficult to reach using conventional techniques.
It is a further object of the present invention to provide a method of introducing a localized resin reinforcement in a structural part where the region to be reinforced is beyond a curvature in a channel.
It is still a further object of the present invention to provide a method of centralizing a resin reinforcement in a hollow structural part in a region which is difficult to access.